Evaluation of Frequency Ratio Method for Groundwater Potential Mapping at Al-Shtar Plain, Lorestan Province

Groundwater is the major sources of fresh water supply for human being. Iran country with arid and semi-arid climate conditions and average annual rainfall of 250 ml is considered as one of the most waterless countries of the world. In this study, the frequency ratio method on the basis of GIS was used for detection and zoning of the Al-shtar plain regions which are potential in terms of underground waters in Lorestan Province. The most initial step is identification of effective factors. So, seven effective factors including gradient, altitudinal floors, land use, curvature of the earth, Standardized Precipitation Index (SPI), Topographic Wetness Index were identified and documented with regard to the resources review. For this purpose, among from the 28 available wells, 20 wells were selected for education and calibration of the model and 8 wells were utilized for validation. The associated map to the 5 classes with so low, low, average, high and very high potential was categorized. According to the performed validation, the frequency ratio model has enough accuracy and it is suitable for preparation of potential detection maps of underground water supply of Al-shtar plain. The results demonstrated that the western and northern edge of the plain have high potential, while the center of the plain has average potential.